Ingredients

  • 1 6- to 7-pound leg of lamb, trimmed
  • Coarse salt and freshly ground pepper
  • 2 garlic cloves, thinly sliced
  • 2 tablespoons plus 2 teaspoons Dijon mustard
  • 2 tablespoons chopped fresh thyme, plus 1 bunch for pan and garnish
  • 1 tablespoon chopped fresh rosemary, plus 1 bunch for pan and garnish
  • 2 tablespoons extra-virgin olive oil
  • 2 onions, peeled and quartered
  • 4 carrots, peeled
  • 4 stalks celery
  • 6 new potatoes, halved if large
  • 2 tablespoons all-purpose flour
  • 2 tablespoons unsalted butter, softened
  • 1/2 cup dry red wine
  • 1 cup homemade or low-sodium store-bought beef stock

Method

  • Preheat the oven to 500F.
  • Season the lamb with salt and pepper.
  • Make 1-inch slits all over; place a sliver of garlic in each.
  • Rub 2 tablespoons mustard over the lamb; coat evenly with the thyme and rosemary, patting gently.
  • Rub the oil over the bottom of a roasting pan; cover with herb bunches.
  • Place the lamb on top.
  • Roast 20 minutes; reduce heat to 375F.
  • Add the onions, carrots, celery, and potatoes; season with salt and pepper.
  • Roast until a meat thermometer inserted near center, avoiding bone, reads 140F, about 70 minutes.
  • Transfer the lamb and vegetables to a platter; let rest 20 minutes.
  • Meanwhile, make the sauce: Knead the flour and butter together.
  • Pour off the fat; place the pan over medium heat.
  • Add the wine; reduce by half.
  • Add the remaining mustard and stock.
  • Stir; reduce slightly.
  • Strain into a saucepan; simmer.
  • Add the butter mixture in small pieces, whisking constantly.
  • Remove from heat; season with salt and pepper.
  • Garnish with herbs.